Image sensor including nanostructure color filter

ABSTRACT

An image sensor includes a first light sensor layer including light sensing cells configured to sense first light of an incident light and generate electrical signals based on the sensed first light, and a color filter array layer disposed on the first light sensor layer, and including color filters respectively facing the light sensing cells. The image sensor further includes a second light sensor layer disposed on the color filter array layer, and configured to sense second light of the incident light and generate an electrical signal based on the sensed second light. Each of the color filters includes a nanostructure including a first material having a first refractive index, and a second material having a second refractive index greater than the first refractive index, the first material and the second material being alternately disposed with a period.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims priority from U.S. Provisional Application No.62/315,284, filed on Mar. 30, 2016, in the U.S. Patent and TrademarkOffice, and Korean Patent Application No. 10-2016-0149555, filed on Nov.10, 2016, in the Korean Intellectual Property Office, the disclosures ofwhich are incorporated herein by reference in their entireties.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

This invention was made with government support under Grant No. 1512266awarded by the National Science Foundation. The government has certainrights in the invention.

BACKGROUND

1. Field

Apparatuses relate to an image sensor including a nanostructure colorfilter.

2. Description of the Related Art

The number of pixels in an image sensor is on an increasing trend. Pixelminiaturization is performed to include more pixels with respect to anarea of the image sensor. Issues regarding pixel miniaturization aresecuring pixel intensity and eliminating noise. Recently, with theintroduction of a back illuminated structure (BIS) sensor of a cellseparation type, much progress has been achieved in relation to theseissues.

However, a structure including optical components that collect colorlight proceeding toward an optical sensor, such as a color filter and amicro-lens, is one of the marginal factors of the pixel miniaturization.A thickness of the color filter of an absorption type and a thickness ofthe micro-lens, which is placed on the color filter and guides lighttoward the color filter, are some of the constraint factors.

SUMMARY

Example embodiments may address at least the above problems and/ordisadvantages and other disadvantages not described above. Also, theexample embodiments are not required to overcome the disadvantagesdescribed above, and may not overcome any of the problems describedabove.

An image sensor including a color filter having a structure adequate forpixel miniaturization is provided.

According to an aspect of an example embodiment, there is provided animage sensor including a first light sensor layer including lightsensing cells configured to sense first light of an incident light andgenerate electrical signals based on the sensed first light, and a colorfilter array layer disposed on the first light sensor layer, andincluding color filters respectively facing the light sensing cells. Theimage sensor further includes a second light sensor layer disposed onthe color filter array layer, and configured to sense second light ofthe incident light and generate an electrical signal based on the sensedsecond light. Each of the color filters includes a nanostructureincluding a first material having a first refractive index, and a secondmaterial having a second refractive index greater than the firstrefractive index, the first material and the second material beingalternately disposed with a period.

The sensed second light may have a first color, the color filters mayinclude a first color filter configured to selectively transmit thirdlight having a second color, and a second color filter configured toselectively transmit fourth light having a third color, and the firstcolor filter and the second color filter may respectively includenanostructures having different periods.

A fill factor of the second material included in the first color filtermay be different from a fill factor of the second material included inthe second color filter.

The color filter array layer may further include a first substrateincluding a third material having a third refractive index less than thesecond refractive index, and the nanostructure may be disposed on thefirst substrate.

The color filter array layer may further include a second substrateincluding a fourth material having a fourth refractive index less thanthe second refractive index, and the nanostructure may be interposedbetween the first substrate and the second substrate.

The first material may include one of polymer and silicon dioxide(SiO₂), and the second material may include one of silicon (Si), siliconnitride (Si₃N₄), gallium phosphide (GaP), titanium dioxide (TiO₂),aluminum antimony (AlSb), aluminum arsenide (AlAs), aluminum galliumarsenide (AlGaAs), aluminum gallium indium phosphide (AlGaInP), boronphosphide (BP), and zinc-germanium diphosphide (ZnGeP₂).

The first material and the second material may be two-dimensionallyalternately disposed.

Two directions of the nanostructure included in each of pixels of theimage sensor may vary based on a location of each of the pixels.

The second material may have a stripe shape structure that isone-dimensionally repeatedly disposed, and a longitudinal direction ofthe stripe shape structure of the nanostructure included in each ofpixels of the image sensor may vary based on a location of each of thepixels.

Each of the light sensing cells may include an inorganic photodiode, andthe second light sensor layer may include an organic photodiode.

A fill factor may denote an area ratio of the second material includedin the nanostructure included in each of pixels of the image sensor, andvary based on a location of each of the pixels.

Shapes and arrangements of the first material and the second materialmay be such that the nanostructure collects incident light.

The second refractive index may be greater than the first refractiveindex by about 1.5 or more.

According to an aspect of an example embodiment, there is provided animage sensor including a first light sensor layer including lightsensing cells configured to sense first light of an incident light andgenerate electrical signals based on the sensed first light, and asecond light sensor layer disposed on the first light sensor layer, andconfigured to sense second light of the incident light and generate anelectrical signal based on the sensed second light. The image sensorfurther includes a color filter array layer disposed on the second lightsensor layer, and including color filters respectively corresponding tothe light sensing cells, and each of the color filters may include ananostructure including a first material having a first refractive indexand a second material having a second refractive index greater than thefirst refractive index, the first material and the second material beingalternately disposed with a period.

The sensed second light may have a first color, the color filters mayinclude a first color filter configured to selectively absorb or reflectthird light having a second color, and a second color filter configuredto selectively absorb or reflect fourth light having a third color, andthe first color filter and the second color filter may respectivelyinclude nanostructures having different periods.

A fill factor of the second material included in the first color filtermay be different from a fill factor of the second material included inthe second color filter.

The color filter array layer may further include a first substrateincluding a third material having a third refractive index less than thesecond refractive index, and the nanostructure may be disposed on thefirst substrate.

The color filter array layer may further include a second substrateincluding a fourth material having a fourth refractive index less thanthe second refractive index, and the nanostructure may be interposedbetween the first substrate and the second substrate.

The first material may include one of polymer and silicon dioxide(SiO₂), and the second material may include one of silicon (Si), siliconnitride (Si₃N₄), gallium phosphide (GaP), titanium dioxide (TiO₂),aluminum antimony (AlSb), aluminum arsenide (AlAs), aluminum galliumarsenide (AlGaAs), aluminum gallium indium phosphide (AlGaInP), boronphosphide (BP), and zinc-germanium diphosphide (ZnGeP₂).

The first material and the second material may be two-dimensionallyalternately disposed.

Two directions of the nanostructure included in each of pixels of theimage sensor may vary based on a location of each of the pixels.

The second material may have a stripe shape structure that isone-dimensionally repeatedly disposed, and a longitudinal direction ofthe stripe shape structure of the nanostructure included in each ofpixels of the image sensor may vary based on a location of each of thepixels.

Each of the light sensing cells may include an inorganic photodiode, andthe second light sensor layer may include an organic photodiode.

A fill factor may denote an area ratio of the second material includedin the nanostructure included in each of pixels of the image sensor, andmay vary based on a location of each of the pixels.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and/or other aspects will become apparent and more readilyappreciated from the following description of example embodiments, takenin conjunction with the accompanying drawings in which:

FIG. 1 is a diagram of an image sensor according to an exampleembodiment;

FIG. 2 is a cross-sectional view of a pixel of the image sensor of FIG.1, according to an example embodiment;

FIG. 3 is a cross-sectional view of the pixel of the image sensor ofFIG. 1, according to another example embodiment;

FIG. 4 is a perspective view of a color filter for use in a pixel of animage sensor, according to an example embodiment;

FIG. 5 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 6 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 7 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 8 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 9 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 10 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 11 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 12 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 13 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 14 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 15 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment;

FIG. 16 is a perspective view of a color filter for use in a pixel of animage sensor, according to another example embodiment; and

FIG. 17 is a diagram of another structure included in an areacorresponding to one of light sensing cells in the cross-sectional viewof the pixel illustrated in FIG. 2, according to an example embodiment.

DETAILED DESCRIPTION

Reference will now be made in detail to example embodiments, which areillustrated in the accompanying drawings, wherein like referencenumerals refer to like elements throughout. In this regard, the presentembodiments may have different forms and may not be construed as beinglimited to the descriptions set forth herein. Accordingly, the exampleembodiments are described below, by referring to the figures, to explainaspects. Expressions such as “at least one of,” when preceding a list ofelements, modify the entire list of elements and do not modify theindividual elements of the list.

The inventive concept will now be described more fully with reference tothe accompanying drawings, in which example embodiments of the inventiveconcept are shown. Like reference numerals in the drawings denote likecomponents, and sizes of components in the drawings may be exaggeratedfor convenience of explanation. Various changes in form and details maybe made in the example embodiments. In the case in which a positionrelationship between two items is described with the terms “on ˜” or “onthe top of ˜,” one item may be not only directly on the other item whilebeing in contact with the other item but may also be on the other itemwithout being in contact with the other item.

FIG. 1 is a diagram of an image sensor 1000 according to an exampleembodiment.

Referring to FIG. 1, the image sensor 1000 may include a plurality ofpixels 100 according to an example embodiment. Each pixel 100 maycorrespond to a picture element of images outputted from the imagesensor 1000. The number of pixels 100 included in the image sensor 1000may vary depending on a resolution of the image sensor 1000.

FIG. 2 is a cross-sectional view of the pixel 100 of the image sensor1000 of FIG. 1, according to an example embodiment.

Referring to FIG. 2, each pixel 100 of the image sensor 1000 may includea first light sensor layer 120 including a plurality of first and secondlight sensing cells 121 and 122 sensing an incident light and generatingelectrical signals, a color filter array layer 130 placed over the firstlight sensor layer 120 and including a plurality of first and secondcolor filters CF1 and CF2 respectively facing each of the plurality oflight sensing cells, and a second light sensor layer 140 placed over thefirst and second color filters CF1 and CF2, sensing light, andgenerating an electrical signal.

The plurality of first and second light sensing cells 121 and 122included in the first light sensor layer 120 may be respectivelyindependently driven and generate electrical signals proportional to anintensity of light incident on corresponding elements. The first andsecond light sensing cells 121 and 122 may include inorganic photodiodes. However, the example embodiment is not limited thereto. Thefirst and second light sensing cells 121 and 122 may include, in exampleembodiments, charge-coupled device (CCD) sensors or complementarymetal-oxide semiconductor (CMOS) sensors. The first and second lightsensing cells 121 and 122 may sense the incident light regardless of awavelength of the incident light. The first and second light sensingcells 121 and 122 may generate electrical signals in accordance with anintensity of the sensed incident light.

In addition, partition walls comparting the plurality of first andsecond light sensing cells 121 and 122 may be further arranged in thefirst light sensor layer 120. The partition wall may prevent lightobliquely incident on the first and second color filter CF1 and CF2 fromprogressing incorrectly in a direction in which no light sensing cellsrespectively corresponding to the first and second color filters CF1 andCF2 exist. In example embodiments, light incident on the first colorfilter CF1 may be prevented from incorrectly progressing toward thesecond light sensing cell 122 instead of the first light sensing cell121. In other words, the partition walls may reduce cross-talk betweenadjacent light sensing cells.

In addition, a wiring layer 110 for reading electrical signals generatedin the first light sensor layer 120 may be under the first light sensorlayer 120. The wiring layer 110 may include a plurality of metal wires115. An arrangement type of the wiring layer 110 as illustrated isreferred to as a back side illumination (BSI) type. When the pixels 100of the image sensor 1000 are of the BSI type, a moving path of lightbetween the first and second color filters CF1 and CF2 and the firstlight sensor layer 120 may be reduced. Thus, a volume of the pixels 100may be reduced and diffusion of light signals in the wiring layer 110may be prevented.

A color filter array layer 130 including the plurality of first andsecond color filters CF1 and CF2 may be on the first light sensor layer120. Each of the plurality of first and second color filters CF1 and CF2may respectively face each of the plurality of first and second lightsensing cells 121 and 122. In example embodiments, the first colorfilter CF1 may face the first light sensing cell 121. In addition, thesecond color filter CF2 may face the second light sensing cell 122. Thefirst color filter CF1 may filer the wavelength of light incident on thefirst light sensing cell 121 and the second color filter CF2 may filterthe wavelength of light incident on the second light sensing cell 122.In example embodiments, the first color filter CF1 may selectivelytransmit light having a first color among the incident light. Inaddition, the second color filter CF2 may selectively transmit lighthaving a second color. Accordingly, the first light sensing cell 121 maysense light having the first color and the second light sensing cell 122may sense light having the second color. In example embodiments, thecolor filter array layer 130 may further include a third color filterselectively transmitting light a third color. In example embodiments,the first through third color may be any one color of red color, greencolor, and blue color. In example embodiments, a fourth color filterselectively transmitting light having a fourth color may be furtherincluded. In example embodiments, the first through third color maycorrespond to cyan, yellow, and magenta. However, the colorcorrespondence is not limited thereto.

The second light sensor layer 140 may be on the color filter array layer130. The second light sensor layer 140 may sense light having a coloramong incident light L1 and transform the light having the color to anelectrical signal. In example embodiments, the second light sensor layer140 may include an organic photo diode. The organic photo diode mayinclude an organic photoelectric element capable of selectivelyabsorbing the light having the color as a p-type and a fullerence or afullerene dielectric as an n-type. However, the example embodiment isnot limited thereto. In addition, the second light sensor layer 140 mayinclude another sensor composition capable of sensing the light havingthe color and transforming the light having the color to an electricalsignal. In example embodiments, the second light sensor layer 140 maysense color light that has not been filtered by the color filter arraylayer 130 and generating an electrical signal. In example embodiments,when the color filter array layer 130 filters light having the redcolor, light having the green color, and light having the blue color,the second light sensor layer 140 may sense light having wavelengthsdifferent from those of the red color, the green color, and the bluecolor. Thus, components of the red color, the green color, and the bluecolor of the incident light L1 may be incident on the color filter arraylayer 130 and be sensed by the first light sensor layer 120.

FIG. 3 is a cross-sectional view of the pixel 100 of the image sensor1000 of FIG. 1, according to another example embodiment.

Referring to FIG. 3, the pixel 100 of the image sensor 1000 may includethe first light sensor layer 120 including the plurality of first andsecond light sensing cells 121 and 122 sensing light and generatingelectrical signals, the second light sensor layer 140 being on the firstlight sensor layer 120, sensing light, and generating an electricalsignal, and a color filter array layer 150 being on the second lightsensor layer 140 and including the plurality of first and second colorfilters CF1 and CF2 corresponding to each of the plurality of lightsensing cells.

In the example embodiment of FIG. 3, unlike that of FIG. 2, the colorfilter array layer 150 may be on the second light sensor layer 140.Accordingly, light incident on the second light sensor layer 140 may befiltered by the plurality of first and second color filters CF1 and CF2of the color filter array layer 150.

Each of the plurality of first and second color filters CF1 and CF2 maycorrespond to each of the plurality of first and second light sensingcells 121 and 122. In example embodiments, the first color filter CF1may be on the first light sensing cell 121. In addition, the secondcolor filter CF2 may be on the second light sensing cell 122. The firstcolor filter CF1 may filter the wavelength of light incident on thefirst light sensing cell 121 and the second color filter CF2 may filtera wavelength of light incident on the second light sensing cell 122.

Each of the plurality of first and second color filters CF1 and CF2 maybe a complementary filter that selectively absorbs or reflects the lighthaving the color. In example embodiments, the first color filter CF1 mayselectively absorb or reflect light having the first color light. Inaddition, the second color filter CF2 may selectively absorb or reflectlight having the second color. In addition, the second light sensorlayer 140 may sense light having the third color light and transform thethird color light to an electrical signal. In example embodiments, thesecond light sensor layer 140 may include the organic photo diode. Theorganic photo diode may include an organic photoelectric element capableof absorbing selectively the light having the color as a p-type and afullerenes or a fullerene dielectric as an n-type. However, the exampleembodiment is not limited thereto. In addition, the second light sensorlayer 140 may include other sensor composition capable of sending thelight having the color and transforming the light having the color to anelectrical signal.

The first through third colors may be different from each other. Inexample embodiments, the first through third colors may correspond toany one color of the red color, the green color, and the blue color. Inexample embodiments, the first through third colors may also correspondto any one color of cyan, yellow, and magenta.

In example embodiments, the first color filter CF1 may selectivelyabsorb or reflect red color light. In addition, the second color filterCF2 may selectively absorb or reflect blue color light. In addition, thesecond light sensor layer 140 may sense green color light and generatean electrical signal. Because the red color light is filtered in thefirst color filter CF1 and the green color light is sensed by the secondlight sensor layer 140, the first light sensing cell 121 may sense theblue color light. In addition, because the blue color light is filteredin the second color filter CF2 and the green color light is sensed bythe second light sensor layer 140, the second light sensing cell 122 maysense the red color light. In other words, the second light sensor layer140, and the first and second light sensing cells 121 and 122 mayrespectively sense lights having different colors from each other, andthus, a color image of the pixel 100 may be outputted.

In example embodiments, the color filter array layer 130 in the pixel100 of the image sensor 1000 may include a nanostructure to theplurality of first and second color filters CF1 and CF2 for reducingthickness thereof. In other words, each of the plurality of first andsecond color filters CF1 and CF2 may include a nanostructure thatincludes two materials having different refractive indices from eachother, being repeatedly arranged at a period. Below, detaileddescriptions on this issue will be provided with reference to FIG. 4.

FIG. 4 is a perspective view of a color filter 1 for use in the firstand second color filters CF1 and CF2 included in the pixel 100 of theimage sensor 1000, according to an example embodiment.

The color filter 1 may include high refractive index materials HM1repeatedly arranged at a period T on a substrate S1. The high refractiveindex materials HM1 are illustrated as having a hexahedral block shape.However, the example embodiment is not limited thereto, and may havevarious shapes such as a polyhedral pillar and a cylinder. In addition,the high refractive index materials HM1 are illustrated as beingtwo-dimensionally arranged with rows and columns aligned each other, butthe high refractive index materials HM1 on each row or column may bezigzagged from each other.

An area between the high refractive index materials HM1 may be an emptyspace, in example embodiments, a space including air, and include astructure in which the high refractive index materials HM1 and a lowrefractive index material, that is, the air are alternately arranged.This structure may transmit light having a wavelength that is determinedby a difference between refractive indices of the high refractive indexmaterial HM1 and the low refractive index material, the period T, theshape, thickness of the high refractive index material HM1, etc., andmay absorb or reflect other remaining lights.

The first and second color filters CF1 and CF2 of the pixel 100 of FIG.4 may include the structure of the color filter 1 illustrated in FIG. 4.In addition, the nanostructures of the first and second color filtersCF1 and CF2 may be different from each other in any one or anycombination of the period T, the material, the shape, and thickness suchthat the first color filter CF1 transmits light having the first colorand the second color filter CF2 transmits light having the second color.In example embodiments, the material and the shape of the highrefractive index material HM1 may be same in the first and second colorfilters CF1 and CF2, while the period T or a thickness Th of the firstand second color filters CF1 and CF2 may be differently controlled suchthat a selection of wavelength ranges is respectively controlled.

The period T may be less than a wavelength A of light transmitted by thefirst and second color filters CF1 and CF2 and may be, in exampleembodiments, equal to or less than about ⅔ or about ½ of the wavelengthA. The thickness Th of the high refractive index material HM1 may beless than the wavelength A, in example embodiments, being equal to orless than about ½ of the wavelength A. Herein, the wavelength λ maydenote a center wavelength of a wavelength range selected for beingtransmitted, absorbed, or reflected.

In example embodiments below, a structure including a high refractiveindex material and a low refractive material having a period andthickness less than a wavelength will be denoted as a nanostructure.

The high refractive index material HM1 may include any one of singlecrystal silicon, polycrystalline silicon, amorphous silicon, siliconnitride (Si₃N₄), gallium phosphide (GaP), titanium dioxide (TiO₂),aluminum antimony (AlSb), aluminum arsenide (AlAs), aluminum galliumarsenide (AlGaAs), aluminum gallium indium phosphide (AIGaInP), boronphosphide (BP), and zinc-germanium diphosphide (ZnGeP₂).

The substrate S1 may be a supporting member for forming thenanostructure. The substrate S1 may include a material having a lessrefractive index than the high refractive index material HM1. In exampleembodiments, the substrate S1 may include any one of polymers such aspolycarbonate (PC), polystyrene (PS), and polymethyl methacrylate(PMMA), and SiO₂.

FIG. 5 is a perspective view of a color filter 2 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 2 may include the substrate S1, the high refractiveindex materials HM1 periodically repeatedly arranged on the substrate 1,and a low refractive index material LM1 filling the area between thehigh refractive index materials HM1. This structure may be formed in ashape in which a plurality of through-holes TH are formed in the lowrefractive index material LM1 and the high refractive index materialsHM1 fill the inside of the through-holes. According to another exampleembodiment, after pillars having the high refractive index materials HM1have been formed, the low refractive index material LM1 may fill thespace between the high refractive index materials HM1.

The low refractive index material LM1 may include a material having aless refractive index than the high refractive index material HM1. As anexample, the refractive index of the high refractive index material HM1may be greater than that of the low refractive index material LM1 by afactor of about 1.5 or more. However, the example embodiment is notlimited thereto. In example embodiments, the low refractive indexmaterial LM1 may include any one of polymers such asPolydimethylsiloxane (PDMS), SU-8, hydrogen silsesquioxane (HSQ), andPMMA, and SiO₂.

The substrate S1 may include a material having a less refractive indexthan the high refractive index material HM1. In example embodiments, thesubstrate may include any one of polymers such as PDMS, SU-8, HSQ, andPMMA, and SiO₂. The substrate S1 and the low refractive index materialLM1 may include same materials or different materials from each other.

FIG. 6 is a perspective view of a color filter 3 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

In example embodiments, the color filter 3 may be different from thecolor filter 1 illustrated in FIG. 4 from a point that a substrate S2 isfurther arranged on the high refractive index materials HM1. Thesubstrate S2 may include a material having a less refractive index thanthe high refractive index material HM1, in example embodiments, any oneof polymers such as PDMS, SU-8, HSQ, and PMMA, and SiO₂.

FIG. 7 is a perspective view of a color filter 4 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

In example embodiments, the color filter 4 may be different from thecolor filter 2 illustrated in FIG. 5 from a point that the substrate S2is further arranged on the high refractive index materials HM1. Thesubstrate S2 may include a material having a less refractive index thanthe high refractive index material HM1, in example embodiments, any oneof polymers such as PDMS, SU-8, HSQ, and PMMA, and SiO₂. The substrateS2 and the low refractive index material LM1 may include same materialsor different materials from each other.

FIG. 8 is a perspective view of a color filter 5 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 5 may include the substrate S1 and a high refractiveindex material HM2 having the plurality of through-holes TH therein. Thethrough-hole TH may be an empty space, in example embodiments, an airspace. The high refractive index material HM2 may include any one ofsingle crystal silicon, polycrystalline silicon, amorphous silicon,Si₃N₄, GaP, TiO₂, AlSb, AlAs, AlGaAs, AlGaInP, BP, and ZnGeP₂. Thenanostructure having the low refractive index material and the highrefractive index material alternately arranged therein may be formed bythe air and the high refractive index material HM2.

FIG. 9 is a perspective view of a color filter 6 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 6 may be different from the color filter 5 of FIG. 8from a point that the through-holes TH of the color 5 of FIG. 8 arefilled with a low refractive index material LM2. The low refractiveindex material LM2 may include a material having a less refractive indexthan the high refractive index material HM2, in example embodiments, anyone of polymers such as PDMS, SU-8, HSQ, and PMMA, and SiO₂.

FIG. 10 is a perspective view of a color filter 7 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

In example embodiments, the color filter 7 may be different from thecolor filter 5 illustrated in FIG. 8 from a point that the substrate S2is further arranged on the high refractive index materials HM2.

FIG. 11 is a perspective view of a color filter 8 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

In example embodiments, the color filter 8 may be different from thecolor filter 6 illustrated in FIG. 9 from a point that the substrate S2is further arranged on the high refractive index materials HM2.

FIG. 12 is a perspective view of a color filter 9 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 9 according to an example embodiment may be differentfrom other color filters according to other example embodiments from apoint that the fill factor is not uniform. The fill factor may be anarea ratio of a high refractive index material HM3 in the nanostructureand denote a ratio of an area of the high refractive index material HM3over an entire area based on a light receiving area, that is, an area inparallel with the substrate S1.

The high refractive index material HM3 may include any one of singlecrystal silicon, polycrystalline silicon, amorphous silicon, Si₃N₄, GaP,TiO₂, AlSb, AlAs, AlGaAs, AlGaInP, BP, and ZnGeP₂. A low refractiveindex material LM3 may include a material having a less refractive indexthan the high refractive index material HM3, in example embodiments, anyone of polymers such as PDMS, SU-8, HSQ, and PMMA, and SiO₂.

When the light having the wavelength among the incident light istransmitted, directivity thereof may be controlled by controlling thefill factor. In example embodiments, when light is incident on the firstlight sensor layer 120 in FIG. 2 after having transmitted the colorfilter 9, a light collecting effect toward corresponding light sensingcells may be enhanced. FIG. 12 illustrates that an area occupied by thelow refractive index material LM3 at a center portion is increased forreducing the fill factor and that the area occupied by the lowrefractive index material LM3 on a periphery is reduced for increasingthe fill factor. However, the illustration is an example of controllingthe directivity of transmitted light by controlling the fill factor, andthe example embodiment is not limited thereto. In example embodiments,shapes and arrangements of the material having the first refractiveindex and the material having the second refractive index may bedetermined such that the nanostructure collects light incident thereon.Because the nanostructure performs a function of collecting light, amicro-lens may be omitted in the pixel 100 of the image sensor 1000.

A change in the fill factor may vary depending on which one of thepixels 100 the color filter is included in. In other words, the fillfactor and the shape of the nanostructure of the color filter 9 includedin the pixel 100 may vary depending on a location of the pixel 100. Adifference in the incident angle of the incident light with respect tothe location of the pixel 100 may be corrected by varying the fillfactor and the shape of the nanostructure of the color filter 9 includedin the pixel 100 with respect to the location of the pixel 100.

The color filter 9 of FIG. 12 is illustrated as having a different fillfactor from that of the color filter 6 of FIG. 8, but this illustrationis an example and the change in the fill factor may be similarly appliedto the color filters 1 through 8 in FIGS. 4 through 11.

Referring to FIGS. 4 through 12, examples of two-dimensional alternatearrangements of the material having the first refractive index and thematerial having the second refractive index are illustrated.Two-dimensional directions may vary depending on the location of thepixel 100. In other words, an arrangement direction of the nanostructuremay vary as two directions forming the two-dimension in thenanostructure vary depending on the location of the pixel 100. Thedifference in the incident angle of the incident light with respect tothe location of the pixel 100 may be corrected by varying the twodirections forming the two-dimension in the nanostructure.

FIG. 13 is a perspective view of a color filter 10 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 10 may be different from previously-described exampleembodiments from a point that a high refractive index material HM4 isone-dimensionally repeatedly arranged. The high refractive indexmaterial HM4 may have a protruding type in a stripe shape and berepeatedly arranged in a direction different from the stripe direction.In example embodiments, the stripe shape may be repeatedly arranged in adirection perpendicular to the stripe direction. However, the exampleembodiment is not limited thereto. An area between the high refractiveindex materials HM4 may be an empty space, that is, the air space. Thehigh refractive index material HM4 may include any one of single crystalsilicon, polycrystalline silicon, amorphous silicon, Si₃N₄, GaP, TiO₂,AlSb, AlAs, AlGaAs, AlGaInP, BP, and ZnGeP₂.

FIG. 14 is a perspective view of a color filter 11 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 11 according to an example embodiment may be differentfrom the color filter 10 of FIG. 13 from a point that the area betweenthe high refractive index materials HM4 is filled with a low refractiveindex material LM4. The low refractive index material LM4 may include amaterial having a less refractive index than the high refractive indexmaterial HM4, in example embodiments, any one of polymers such as PDMS,SU-8, HSQ, and PMMA, and SiO₂.

FIG. 15 is a perspective view of a color filter 12 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 12 according to an example embodiment may be differentfrom the color filter 10 of FIG. 13 from a point that the substrate S2is further arranged on the high refractive index material HM4.

FIG. 16 is a perspective view of a color filter 13 for use in the pixel100 of the image sensor 1000, according to another example embodiment.

The color filter 13 according to an example embodiment may be differentfrom the color filter 11 of FIG. 14 from a point that the substrate S2is further arranged on the high refractive index material HM4.

Referring to FIGS. 13 through 16, the material having the secondrefractive index may form a structure having the stripe shape in thenanostructure of the color filters 10 through 13 and the structurehaving the stripe shape may be one-dimensionally repeatedly arranged. Alongitudinal direction of the structure having the stripe shape may varywith respect to the pixel 100. In other words, the arrangement directionof the nanostructure may vary as the longitudinal direction of thestructure having the stripe shape in the nanostructure varies withrespect to the location of the pixel 100. The difference in the incidentangle of the incident light with respect to the location of the pixel100 may be corrected by varying the longitudinal direction of thestructure having the stripe shape in the nanostructure with respect tothe pixel 100.

FIG. 17 is a diagram of another structure included in an areacorresponding to one of the first and second light sensing cells 121 and122 in the cross-sectional view of the pixel 100 illustrated in FIG. 2,according to an example embodiment.

Referring to FIG. 17, the incident light L1 may be incident on thesecond light sensor layer 140. The second light sensor layer 140 maysense the light having the first color. When the second light sensorlayer 140 senses the light having the first color, the second lightsensor layer 140 may accumulate electric charges generated via aphotoelectric effect. The electrical signal may be transferred by amovement of the electrical charges generated in the second light sensorlayer 140. In example embodiments, a through-channel 116 may be underthe second light sensor layer 140 for the movement of the electricalcharges. The through-channel 116 may pass through the wiring layer 110.The through-channel 116 may be connected to a wire 118 on a bottom sideof the wiring layer 110 via a gate 117. The electrical signal generatedin the second light sensor layer 140 may be transferred to the wire 118on the bottom side of the wiring layer 110 via the through-channel 116.In addition, the electrical signal generated in the first and secondlight sensing cells 121 and 122 may be transferred to a wire 114 on thebottom side of the wiring layer 110 via a transfer gate 112.

According to the above example embodiments, because opticalcharacteristics of a color filter of an image sensor are determined by aperiod, shape, an arrangement, etc. of a nanostructure, a properstructure condition for a wavelength or an incident angle may bederived. Thus, wavelength selectivity may be enhanced and controllingcolor bandwidth may be easy. In addition, thickness of the color filtermay be less than the wavelength of light by realization of the colorfilter having a nanostructure. Thus, a micro-lens may be omitted frompixels of the image sensor by designing the nanostructure in a way thatthe color filter functions as the micro-lens. Accordingly, the pixel ofthe image sensor may be miniaturized.

Descriptions on the image sensor 1000 according to the above exampleembodiments have been provided with reference to FIGS. 1 through 17.According to the above example embodiments, because the opticalcharacteristics of the color filter included in the image sensor 1000are determined by the period, the shape, the arrangement, etc. of thenanostructure, the structure suitable for the wavelength or the incidentangle may be determined. Thus, the wavelength selectivity may beenhanced and controlling color bandwidth may be easy. In addition, thethickness of the color filter may be less than the wavelength of lightby realization of the color filter having the nanostructure. Thus, themicro-lens may be omitted from the pixel 100 of the image sensor 1000 bydesigning the nanostructure in a way that the color filter functions asthe micro-lens. Accordingly, the pixel 100 of the image sensor 1000 maybe miniaturized.

It may be understood that example embodiments described herein may beconsidered in a descriptive sense only and not for purposes oflimitation. Descriptions of features or aspects within each exampleembodiment may typically be considered as available for other similarfeatures or aspects in other example embodiments.

While example embodiments have been described with reference to thefigures, it will be understood by those of ordinary skill in the artthat various changes in form and details may be made therein withoutdeparting from the spirit and scope as defined by the following claims.

What is claimed is:
 1. An image sensor comprising: a first light sensorlayer comprising light sensing cells configured to sense light that isincident on the light sensing cells, and generate electrical signalsbased on the sensed light that is incident on the light sensing cells; acolor filter array layer disposed on the first light sensor layer, andcomprising color filters respectively facing the light sensing cells;and a second light sensor layer disposed on the color filter arraylayer, and configured to sense light that is incident on the secondlight sensor layer, and generate an electrical signal based on thesensed light that is incident on the second light sensor layer, whereinthe light sensed by the second light sensor layer has a first color,each of the color filters comprises a nanostructure comprising firstmaterials having a first refractive index, and second materials having asecond refractive index greater than the first refractive index, thefirst materials and the second materials being alternately disposed witha period, the color filters comprise a first color filter configured toselectively transmit light having a second color, and a second colorfilter configured to selectively transmit light having a third color,the first color, the second color, and the third color are differentfrom each other, the color filter array layer performs a function ofcollecting light, the period is less than a wavelength of light that isincident on the color filter array layer, and each of a thickness of thefirst materials and a thickness of the second materials is less than thewavelength of the light that is incident on the color filter arraylayer.
 2. The image sensor of claim 1, wherein the first color filterand the second color filter respectively comprise nanostructures havingdifferent periods.
 3. The image sensor of claim 1, wherein each of thefirst color filter and the second color filter performs a function ofcollecting light.
 4. The image sensor of claim 1, wherein the colorfilter array layer further comprises a first substrate comprising athird material having a third refractive index less than the secondrefractive index, and the nanostructure is disposed on the firstsubstrate.
 5. The image sensor of claim 4, wherein the color filterarray layer further comprises a second substrate comprising a fourthmaterial having a fourth refractive index less than the secondrefractive index, and the nanostructure is interposed between the firstsubstrate and the second substrate.
 6. The image sensor of claim 1,wherein the first materials comprise one of polymer and silicon dioxide(SiO₂), and the second materials comprises one of silicon (Si), siliconnitride (Si₃N₄), gallium phosphide (GaP), titanium dioxide (TiO₂),aluminum antimony (AlSb), aluminum arsenide (AlAs), aluminum galliumarsenide (AlGaAs), aluminum gallium indium phosphide (AlGaInP), boronphosphide (BP), and zinc-germanium diphosphide (ZnGeP₂).
 7. The imagesensor of claim 1, wherein the first materials and the second materialsare two-dimensionally alternately disposed.
 8. The image sensor of claim1, wherein two directions of the nanostructure included in each ofpixels of the image sensor vary based on a location of each of thepixels.
 9. The image sensor of claim 1, wherein the second materialshave a stripe shape structure that is one-dimensionally repeatedlydisposed, and a longitudinal direction of the stripe shape structure ofthe nanostructure included in each of pixels of the image sensor variesbased on a location of each of the pixels.
 10. The image sensor of claim1, wherein each of the light sensing cells comprises an inorganicphotodiode, and the second light sensor layer comprises an organicphotodiode.
 11. The image sensor of claim 1, wherein the fill factordenotes an area ratio of the second materials included in thenanostructure included in each of pixels of the image sensor, and variesbased on a location of each of the pixels.
 12. The image sensor of claim1, wherein shapes and arrangements of the first materials and the secondmaterials are such that the nanostructure collects incident light. 13.The image sensor of claim 1, wherein the second refractive index isgreater than the first refractive index by about 1.5 or more.
 14. Theimage sensor of claim 1, wherein the nanostructure comprisesthrough-holes disposed through the second materials, and the secondmaterials comprise air spaces within the through-holes.
 15. The imagesensor of claim 1, wherein the nanostructure comprises through-holesdisposed through the second materials, and the first materials aredisposed within the through-holes.
 16. An image sensor comprising: afirst light sensor layer comprising light sensing cells configured tosense light that is incident on the light sensing cells, and generateelectrical signals based on the sensed light that is incident on thelight sensing cells; a second light sensor layer disposed on the firstlight sensor layer, and configured to sense light that is incident onthe second light sensor layer, and generate an electrical signal basedon the sensed light that is incident on the second light sensor layer;and a color filter array layer disposed on the second light sensorlayer, and comprising color filters respectively corresponding to thelight sensing cells, wherein the light sensed by the second light sensorlayer has a first color, each of the color filters comprises ananostructure comprising first materials having a first refractive indexand second materials having a second refractive index greater than thefirst refractive index, the first materials and the second materialsbeing alternately disposed with a period, the color filters comprise afirst color filter configured to selectively absorb or reflect lighthaving a second color, and a second color filter configured toselectively absorb or reflect light having a third color, the firstcolor, the second color, and the third color are different from eachother, the color filter array layer performs a function of collectinglight, the period is less than a wavelength of light that is incident onthe color filter array layer, and each of a thickness of the firstmaterials and a thickness of the second materials is less than thewavelength of the light that is incident on the color filter arraylayer.
 17. The image sensor of claim 16, wherein the first color filterand the second color filter respectively comprise nanostructures havingdifferent periods.
 18. The image sensor of claim 16, wherein each of thefirst color filter and the second color filter performs a function ofcollecting light.
 19. The image sensor of claim 16, wherein the colorfilter array layer further comprises a first substrate comprising athird material having a third refractive index less than the secondrefractive index, and the nanostructure is disposed on the firstsubstrate.
 20. The image sensor of claim 19, wherein the color filterarray layer further comprises a second substrate comprising a fourthmaterial having a fourth refractive index less than the secondrefractive index, and the nanostructure is interposed between the firstsubstrate and the second substrate.
 21. The image sensor of claim 16,wherein the first materials comprise one of polymer and silicon dioxide(SiO₂), and the second materials comprises one of silicon (Si), siliconnitride (Si₃N₄), gallium phosphide (GaP), titanium dioxide (TiO₂),aluminum antimony (AlSb), aluminum arsenide (AlAs), aluminum galliumarsenide (AlGaAs), aluminum gallium indium phosphide (AlGaInP), boronphosphide (BP), and zinc-germanium diphosphide (ZnGeP₂).
 22. The imagesensor of claim 16, wherein the first materials and the second materialsare two-dimensionally alternately disposed.
 23. The image sensor ofclaim 16, wherein two directions of the nanostructure included in eachof pixels of the image sensor vary based on a location of each of thepixels.
 24. The image sensor of claim 16, wherein the second materialshave a stripe shape structure that is one-dimensionally repeatedlydisposed, and a longitudinal direction of the stripe shape structure ofthe nanostructure included in each of pixels of the image sensor variesbased on a location of each of the pixels.
 25. The image sensor of claim16, wherein each of the light sensing cells comprises an inorganicphotodiode, and the second light sensor layer comprises an organicphotodiode.
 26. The image sensor of claim 16, wherein the fill factordenotes an area ratio of the second materials included in thenanostructure included in each of pixels of the image sensor, and variesbased on a location of each of the pixels.